Compressive fabric



1962 A. BURLESON ETAL 3,069,883

' COMPRESSIVE FABRIC Filed Feb. 3, 1959 INVENTORS ATTORNEYS UnitedStates Patent F 3,069,883 COMPREdSIVE FABRIC Aaron Burleson and Mark N.Holmes, Burlington, N.C., assignors to Burlington Industries, Inc.,Greensboro, NIL, a corporation of Delaware Filed Feb. 3, 195?, Ser. No.790,912 8 Claims. (Cl. 66-178) The present invention relates to knitcompressive fabric and is especially concerned with the provision ofknit support hose for both women and men covering a full range ofsupport. Other knit constructions, in addition to support hose, are alsocontemplated herein, as will be apparent from the ensuing description ofthe invention.

Broadly stated, knit support hose or other compressive fabric accordingto the invention comprise consecutive or spaced courses of covered(wrapped) or uncovered (unwrapped) synthetic elastomer yarn, namely,polyurethane yarn, such as that produced by E. l. du Pont under the nameFiber K and Vyrene by U.S. Rubber. The hose may be knit entirely withthe covered or un covered polyurethane yarn or this yarn may be used incombination with other types of yarns. The compressive action of thehose or other fabric herein can be regulated in various ways, ashereinafter discussed, to provide a full range of support hose, i.e.fully surgical, semi-surgical or moderate support.

A variety of covering yarns may be used, e.g. silk, rayon and cotton butnylon yarn is preferred. The denier of the covering yarn can be varieddepending upon other conditions, e.g. the denier of the core yarn andthe nature of the ultimate product desired. Preferably, a multifilamentcovering yarn free of twist is used although monofilament yarn with orwithout twist may be utilized. Spun yarns may also be used for coveringpurposes. Typically, in the case of a 70 denier polyurethane core yarnfor use in womens hose, especially desirable covering yarn is 40 denier,multifilament nylon yarn which is essentially twist-free or 2/20selasticized yarn (Helanca type).

A desirable feature of the present invention is that the polyurethaneyarn may be wrapped with only a single wrapping layer of covering yarnalthough plural wrapping layers may also be used. In the past, where arubber core yarn has been used for support hose, a double coveringinvolving Wrapping in opposite directions has been essential toeliminate torquing, facilitate dyeing, etc. The Fiber K polyurethanecore yarn used herein, however, is peculiarly adapted for use with asingle wrapping to give good dyeing, hand and other desirablecharacteristics in the finished product.

Support hose or other compressive fabric according to the invention maybe either full-fashioned or seamless, i.e. they may be knit onfull-fashion or circular knitting machines.

As indicated heretofore, the compressive nature of hose or other fabricaccording to the invention can be adjusted in a variety of ways to givea fabric having the desired degree of support. Typically, this may beaccomplished by regulating the degree of fabric tightness, yarn denieror the like. Thus, for example, in the case of circularly knit fabric, awide variation in the degree of compressibility or support may beobtained by changing the cylinder size of a circular knitting machineWhile maintaining a constant number of needles. Alternatively, thenumber of needles may be changed while the cylinder size is kept thesame. With any given cylinder size, it will be recognized that anincrease in the number of needles gives a more tightly knit fabric whichin turn offers greater compressive or supporting action. Similarly, whenusing a fixed number of needles, e.g. 200, a reduction of the cylindersize from, for example, 3%." to

3,059,883 Patented Dec. 25, 1962 3", will give a tighter fabric and,therefore, increased support.

' least some portion of the stocking, e.g. the leg, foot and/or weltsections. However, in lieu of this, the yarn may be alternated withanother yarn, preferably raw or elasticized nylon yarn (Helanca typestretch yarn) so that the polyurethane yarn appears only in spacedcourses in the stocking, the spacing depending upon the ultimate degreeof support desired. Conventional reenforcing type yarns may also beused, as may be desired, in the welt, heel and/ or toe portions, orotherwise.

' The degree of compressibility or support offered by hose or otherfabric prepared according to the invention may also be at leastpartially controlled by the nature of the covering yarn. Normally,polyurethane yarn possesses a stretch of 600700% before wrapping, i.e.the yarn can be stretched to between six and seven times its length inthe untensioned condition. For highly compressive purposes, the yarnshould desirably retain a stretch between 100 and 500%, usually about250%, after the wrapping operation. By knitting tightly, thestretchability of the covered yarn may be reduced by an additional2050%, to exert an even greater compressive force. For semi-surgicalsupport, the wrapped yarn may stretch 200 to 550% of its original lengthand for moderate support purposes, the wrapped yarn may stretch only 300to 600% of such length.

The polyurethane core yarn is preferably wrapped while under tension forthe purposes of the present invention. The amount of wrapping tensionutilized depends upon various other factors, e.g. the degree offluffiness and stretch desired at the end, the number of wraps to beapplied, the degree of support, etc. As noted heretofore, Fiber Kpolyurethane yarn, prior to covering, normally has a 600700% stretch.Preferably, the polyurethane yarn is wrapped under a tension such thatthe core yarn is stretched to between 40% and 90% of its maximum lengthin the fully stretched condition, i.e. to a length between about 2.4 and6.3 times its untensioned length. Usually, from 4 to 24 wraps of thecovering yarn are applied per inch of tensioned core yarn although itwill be recognized that this can be substantially varied.

Sufficient wrapping yarn should be used to eifectively cover the coreyarn when the stocking or other fabric is worn.

After wrapping, the polyurethane yarn does not return completely to itsoriginal untensioned length due to the fact that the covering yarnexerts a slight degree of compression and tension on core. Normally,this means that the covered yarn in its relaxed state, is between about5% and 40% longer than the polyurethane yarn in its original unwrappedcondition.

Knitting of the stocking or other fabric according to the inventionshould also be carried out with the covered polyurethane yarn undertension. Usually, this tension should be sufllcient to stretch the yarnan additional 25 to 200%, typically from its relaxed condition in thecovered state, this being dependent on type of wrap. All otherconditions being the same, an increase in the knitting tension effects acorresponding increase in the compressive action of the stocking orother fabric.

As a typical illustration of operations according to the invention,womens full surgical stockings may be prepared as follows:

70 denier Fiber K polyurethane yarn is wrapped in conventional manner ona hollow spindle machine. The

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yarn is given a single warp of 40 denier, 34 filament raw, i.e.conventional non-stretch, nylon yarn. The wrap is applied twelve wrapsper inch while the core polyurethane yarn is stretched about 60% of itsmaximum stretch, i.e. to about 4 times its length in the untensionedstate. This is equivalent to approximately 30 wraps per inch of thewrapped yarn in the relaxed state. The thus wrapped yarn is then conedat a speed and tension such that the yarn relaxes to about one half ofits original 60% stretch, i.e. the coned yarn is stretched about 30%, orabout twice the length of the yarn in the unwrapped, relaxed state.

The wrapped yarn is then knit on a 340 seamless machine (3 /2 cylinder).The yarn is knit under tension such that it stretches an additional 25%of its total stretch during knitting. The wrapped yarn is knitexclusively throughout the leg of the stocking. The welt, toe and heelare knit with 100* denier multifilament stretch nylon yarn (Helanca)processed yarn as disclosed in US. Patents 2,019,183; 2,019,185; and2,564,245. The resulting product may be dyed, boarded and otherwisefinished to give a highly desirable womens full support stockingcharacterized by its softness and suede-like nature. Typically, whenthis stocking is stretched coursewise and tested conventionally under 1"and 2 stretch, the compressive force in pounds at the knee are about1.50 and 2.25, respectively, and at the ankle, 1.75 and 2.65,respectively.

Instead of using stretch nylon yarn exclusively in the welt, toe andheel portions, one or more of these portions may also be knit throughoutwith the covered polyurethane yarn alone or in combination with stretchor raw nylon or some other yarn. Typically, one or more of theseportions may be knit with alternate courses of polyurethane yarn andstretch nylon yarn.

As a further specific illustration, the procedure outlined above may bemodified by using 2/ 20 stretch nylon yarn (Helanca) or a single 20denier stretch nylon yarn as the wrapping yarn instead of 40/ 30 rawnylon yarn. In this modification, relaxation of the core yarn is furtherlimited because of relaxation of the wrapping yarn. The 40/34 raw nyloncovering yarn allows more relaxation in the core yarn and, therefore,gives a somewhat flufiier and softer stocking. However, the stockingobtained with 2/20 covering yarn or single 20 denier yarn is also verydesirable and gives effective and full support.

While the foregoing illustrates the invention in connection with womensstockings, mens hose covering a full range of support may also be madein accordance with the principles herein disclosed. Typically, such menshose may be knit on a conventional half-hose machine by knitting, forexample, 70 denier, 140 denier or 280 denier polyurethane (Fiber K) yarncovered (wrapped), or uncovered (raw K yarn). The covered (wrapped) yarnmay be covered with raw nylonyarn from 40 to 70 denier or elasticizedyarn (Helanca type) from 2/20 to 2/40 denier applied under tension(equivalent to 50%-60% maximum stretch of the K yarn). The entirestocking or a portion thereof, e.g. the leg portion extending from belowthe knee to the ankle, may be knit with this covered (wrapped) oruncovered (raw) polyurethane yarn with or without other yarns to givethe desired degree of support. The top portion of sock may be knit orlaid in only with covered or uncovered K yarn for the purpose ofsupporting sock.

The various objects and inventive principles herein are. furtherillustrated by the accompanying drawings wherein:

FIGURE 1 is a side elevational view of a finished womens compressivestocking according to the invention;

FIGURE 2 is an enlarged view of the fabric encircled in the stockingshown in FIGURE 1;

FIGURE 3 is an enlarged view of an alternate fabric structure accordingto the invention; and

FIGURE 4 is a sectional view showing the wrapped polyurethane yarn usedherein.

As will be apparent, the stocking S of FIGURE 1 comprises a welt'portion 2, including afterwelt 4, and leg and foot portions 6 and 8,respectively. In FIG- URE 2, the numeral 10 stands for the wrappedpolyurethane yarn knit with the usual loop structure, a single wrap ofnylon yarn or the like being designated at 12 in FIGURE 4, while thepolyurethane core is shown at 14. The fabric of FIGURE 2 comprisesconsecutive courses of wrapped polyurethane yarn and, as indicatedheretofore, this may apply throughout the leg portion of the stockingand/or the welt or foot portions, including the toe, heel and/or solesections of the foot. FIGURE 3 shows an. alternative constructionwherein the fabric is knit with alternating courses of the polyurethaneyarn It and stretch nylon yarn 16 or the like.

It will be appreciated from the foregoing that hosiery or other productsmay be knit according to the invention herein to offer a complete rangeof compressive action or support. As will be apparent, typicalvariations include using the same denier elastomer yarn in every othercourse to knit a tight fabric for full surgical hose and acorrespondingly looser fabric for semiand moderate support having thedesired construction or compression.

Alternatively, it is possible to knit the same tightness of fabric everycourse with the elastomer yarn but, by using a difierent denier ofpolyurethane yarn, to attain the desired construction or compression offabric to cover the range of full surgical, semi-surgical and moderatesupport hose. As a further alternative, it is possible to use the samedenier elastomer yarn throughout and knit every course with this yarnfor full surgical hose; knit alternate courses with this denier yarnusing a Helanca type stretch yarn in the other courses to give asemi-surgical product; and for moderate support hose, the elastomer yarnmay be knit in every third or fourth course using Helanca type orstretch yarn in the other courses. In other words, the compressiveaction may bevaried by regulating the spacing of the polyurethane yarn.

While nylon yarn, stretch or otherwise, is especially desirable for useherein for knitting in combination with the wrapped polyurethane yarn,other yarns, natural or synthetic may be used. T bus, for example,polyurethane tetrephthalate (Dacron) or other synthetic linear poly--ester or polyamide yarns, rayon, cotton, silk, etc., are suitable foruse herein.

The use of polyurethane yarn in the manner described erein offers anumber of unique advantages over prior efforts involving the use ofrubber yarns. For one thing, the polyurethane yarn use-d in the mannerdescribed makes it possible to effectively satisfy a very definite. needfor a range of support hose covering full surgical, semi-surgical andmoderate surgical, for both men and women. Furthermore, the polyurethaneyarn may be satisfactorily used in much smaller deniers, e.g. one-thirdthe denier in weight compared to rubber yarn to give the desired rangeof compressive action or supporting power. Full and semi-surgical hoseaccording to the invention demonstrate sheerer and softercharacteristics and when dyed the appropriate shade, appear much moreskin-like than rubber surgical hose and a regular sheer stocking may beplaced thereover without the tell-tale detection that a surgicalstocking is underneath. The hose demonstrate an improved liveliness thatgives a better and smoother fit. At the same time, the present hose aremore comfortable to wear in that they avoid the clarnmy feeling ofconventional rubber surgica hose. The fabric also effectively hidesblemishes and broken veins.

In addition to providing a full range of support hose for men and women,the invention contemplates-other fabrics wherein some degree ofcompressive action is desirable, such as circularly knit orfull-fashioned tights, leggings or sleeves for angle or knee support orthe like. In such cases, any of the variations heretofore mentioned maybe utilized. Usually, in the case of tights a bigger core yarn andheavier wrap are desirable since less compressive force is necessary.For tights and supports, it is normally preferable to knit or lay in thewrapped or unwrapped polyurethane yarn in combination with stretch yarn(e.g. Helanca type yarn). Such combinations may include spaced oralternating knit courses of the polyurethane yarn and nylon yarnthroughout at least a portion of the fabric, e.g. the legs only oftights. Alternatively, the fabric may include a series of consecutivecourses of polyurethane yarn and a series of consecutive courses ofnylon yarn. The polyurethane yarn may also be knit in such combinationswith nlyon yarn or the like in the heel, sole and/ or toe areas ofconventional full fashioned or seamless hose for the purpose ofimproving boarding and/or the fitting properties of the foot. Ifdesired, the polyurethane yarn described herein may be either knit orlaid in half-hose tops to facilitate retaining the hose in position onthe leg. For this purpose, a 280 denier covered polyurethane yarn laidin is of particular value.

Support hose wherein the polyurethane yarn is laid in are described inour copending applications, Serial No. 749,394, filed July 18, 1958, andnow abandoned, and Serial No. 756,012, filed August 19, 1958, now PatentNo. 2,949,023.

Having described various modifications of the invention, what is claimedherein as new is:

We claim:

1. Support hose comprising knit courses of elastomeric polyurethane yarnthroughout at least the leg portion, said yarn being wrapped withmultifilament stretch nylon yarn.

2. Support hose comprising courses of 70 to 280 denier elastomericnonfoamed polyurethane yarn at least throughout the leg portion of saidhose, said yarn having been wrapped under tension with a single layer ofmultifilament stretch nylon yarn of lower denier within the range ofabout 40 to 140 denier.

3. Support hose comprising polyurethane yarn knit in every coursethroughout the leg portion of said hose, said yarn constituting a singleelastomeric polyurethane core yarn knit under tension and having atleast one layer of different wrapping yarn thereon, said wrapping yarnhaving been applied to said polyurethane core yarn while the latter isin a tensioned condition such that said polyurethane yarn is stretchedto between about 40 and 90% of its maximum stretch in the unwrappedcondition and the wrapped yarn, in its relaxed state, is between about 5and 40% longer than the relaxed yarn before wrapping.

' 4. Mens support hose comprising knit courses of a 7 single 70 to 280denier elastomeric polyurethane core yarn knit under tension throughoutat least the leg portion of said hose, said yarn having been wrappedunder tension with at least one wrapping layer of /34 stretch nylonyarn.

5. Knit tights comprising a body portion and leg portions, said portionsbeing knit essentially throughout with wrapped elastomeric polyurethaneyarn, said yarn comprising a single elastomeric polyurethane core yarnwrapped with stretch yarn and knit under tension.

6. A knit compressive fabric comprising courses of wrapped yarn, saidwrapped yarn comprising a single core of elastomeric polyurethane yarnwrapped under tension with a single layer of multifilament stretch yarndifferent from said core yarn.

7. A knit support garment comprising a tubular support portion havingelastomeric polyurethane yarn knit in all of the stitches in at least asubstantial portion of the courses of said support number, said yarnbeing knitted under substantially constant tension while stretched to alength which is about 25 to 200% greater than the length of the yarn inits relaxed state before knitting.

8. Womens support hose comprising courses of 70 denier elastomericpolyurethane yarn, at least throughout the leg portion, said yarnconstituting a single non-foamed elastomeric core yarn knit undertension and previously wrapped under tension with at least one wrappinglayer of 2/20 stretch nylon yarn applied to the polyurethane yarn whilethe latter is under tension such that said polyurethane yarn isstretched to between about 40 and of its maximum stretch in theunwrapped. condition and the wrapped yarn, in its relaxed state, isbetween about 5 and 40% longer than the relaxed yarn before wrapping.

References Cited in the file of this patent UNITED STATES PATENTS1,759,497 Weintraub May 20, 1930 1,822,847 Adamson Sept. 8, 19312,013,396 Adamson Sept. 3, 1935 2,441,085 Schneider May 4, 19482,625,535 Mastin et a1 Jan. 13, 1953 2,702,998 Purcell Mar. 1, 19552,720,097 De Mond Oct. 11, 1955 2,902,819 Ross Sept. 8, 1959 2,962,885Knohl Dec. 6, 1960 3,001,359 Simon Sept. 26, 1961 FOREIGN PATENTS212,617 Australia Dec. -17, 1957 766,975 France Apr. 23, 1934 1,150,358France Aug. 5, 1957 282,534 Great Britain Dec. 29, 1927 674,989 GreatBritain July 2, 1952 795,538 Great Britain a- May 28, 1958 UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTION Patent Non 3,069,883 December25, 1962 Aaron Burleson et a1,

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 3, line 1 for "warp" read wrap line 40, for "40/30" read 40/34column 5 line 3, for "angle" read ankle column 6, line 18, for "portion"read number line 19, for "number" read portion Signed and sealed this3rd day of September 1963,

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents

